i can't figure out how the guy did it, but take a look at this guys result:
http://racesonline.com/events/littlerockmarathon/results/2015/2377/cat/div/age/gen
And look at his photos:
http://www.racephotonetwork.com/QPPlus/SearchBibNumber.aspx?_AccountNumber=13447&_EventID=1630062
He ran sub 7:00 second half if the results are correct, to get his BQ after opening with a 2:06 half. He hit all the check points though, but in the finishing photos he finishes with 4:30 marathoner?